#include <iostream>
#include <Eigen/Dense>

using namespace std;
using namespace Eigen;

int main()
{
    Matrix2d a;
    a << 1, 2, 3, 4;

    MatrixXd b(2, 2);
    b << 2, 3, 1, 4;

    cout << "a + b = \n"
         << a + b << endl;
    cout << "a - b = \n"
         << a - b << endl;

    cout << "Doing a += b\n"
         << endl;
    a += b;
    cout << "Now a =\n"
         << a << endl;

    Vector3d v(1, 2, 3);
    Vector3d w(1, 0, 0);

    cout << "-v + w - v = \n"
         << -v + w - v << endl;

    return 0;
}
